Subnet Expert

CIDR /18 Subnet Reference

Detailed information about IPv4 /18 subnets

/18 Subnet Details

A /18 network provides thousands of usable IP addresses, making it suitable for medium to large organizations or campus networks.

Key Information

CIDR Notation/18
Subnet Mask255.255.192.0
Binary Subnet Mask11111111 11111111 11000000 00000000

Host Information

Total Addresses16,384
Usable Hosts (Standard)16,382
AWS Usable IPs16,377
Azure Usable IPs16,377
GCP Usable IPs16,378

Using /18 in Networks

A CIDR /18 subnet has 16,382 usable IP addresses for hosts. This is a relatively large subnet that can be further divided into smaller subnets if needed.

This subnet size strikes a balance between address space efficiency and management overhead.

Cloud Provider Considerations

Cloud providers reserve some IP addresses in each subnet for internal use, resulting in fewer usable IPs:

  • AWS: 16,377 usable IPs(reserves 5 IPs per subnet)
  • Azure: 16,377 usable IPs(reserves 5 IPs per subnet)
  • GCP: 16,378 usable IPs(reserves 4 IPs per subnet)

When planning your cloud infrastructure, consider these reserved addresses to accurately size your subnets.

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Other CIDR References

/0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/19/20/21/22/23/24/25/26/27/28/29/30/31/32
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